We should have a system where you can buy crates with in game currency, and maybe also a system where you can buy crates with real money on the website (real money crate purchases would give people a good reason to donate.)

Buying crates with IRL money used to be a thing, and there were a lot of purchases. So if we brought them back, we could make more money for the server.

However I am not sure if such a purchase is valid to the EULA due to giving them an advantage because of giving them more crates to get higher gun experience, but we can get those crates by playing.

I don't recommend it at all at this point. Gamers nowadays hate anything that's a loot box due to the EA scandal, etc. (In which that'll include me.) If you feel someone hasn’t earned what they’ve got or they’ve got a better weapon just because they paid for it and you worked for yours, that creates friction.